PHP 5.4 + Oracle 11.2g:在游标中返回集合

Assume, in Oracle 11.2g

the following type:

create type a_type is table of varchar2(30);

the following record type:

type a_record is record(id              number(18)
                       ,a_collection    a_type
                       );

the following cursor type:

type a_cursor is ref cursor return a_record;

the following stored proc definition

function a_function return a_cursor;

When executing the function from PHP 5.4 to retrieve the cursor, I get:

ORA-00932: inconsistent datatypes: expected CHAR got ADT

While I know that collections can be returned individually using:

oci_new_collection
oci_bind_by_name

...it appears that the problem is caused by the inclusion of a_collection in the cursor.

My question is: Does anyone know whether a way exists to return a_collection in a PHP 5.4 cursor from Oracle 11.2g?